[HN Gopher] Identifying banknote fingerprints can stop counterfe...
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       Identifying banknote fingerprints can stop counterfeits on streets
        
       Author : sizzle
       Score  : 16 points
       Date   : 2021-03-24 19:45 UTC (3 hours ago)
        
 (HTM) web link (warwick.ac.uk)
 (TXT) w3m dump (warwick.ac.uk)
        
       | w0mbat wrote:
       | So in the actual article they prove they can tell one real PS10
       | note from another real PS10 note, because every plastic note
       | accidentally has a unique random texture.
       | 
       | But as these are real notes, they can be uniquely identified by
       | the serial number anyway.
       | 
       | They never get to a part where they explain how this technique is
       | useful in telling real notes from fake, since fake plastic notes
       | would also have unique textures.
        
         | readflaggedcomm wrote:
         | Yes, they left out that part. The paper's abstract ends with:
         | 
         | >[Our method] ensures that even in the extreme case when
         | counterfeiters have procured the same printing equipment and
         | ink as used by a legitimate government, counterfeiting
         | banknotes remains infeasible because of the difficulty to
         | replicate a stochastic manufacturing process.
         | 
         | Which means each note manufacturer has its own signature,
         | though whether the researchers confirmed that with more than
         | random samples from circulation, I haven't been able to tell.
         | The full paper is here: https://arxiv.org/abs/2103.06184
        
         | wizzwizz4 wrote:
         | Associate the fingerprint with the ID in the "what money have
         | we issued?" database, probably. This sounds like a more
         | practical version of my "use leaves as money" idea, and that's
         | what I did. The impressive part of this research is realising
         | that there might be a pre-existing "fingerprint", and finding a
         | way of looking at it. They probably assumed "how this is
         | useful" was obvious.
        
         | dcroley wrote:
         | They would keep a DB of the note fingerprints and look them up
         | in that. Thus, this would only work if online or something.
        
         | Aachen wrote:
         | You can counterfeit that serial number. It's much harder,
         | perhaps neigh impossible, to counterfeit this fingerprint. Thus
         | a database of existing fingerprints tells you whether it's real
         | or counterfeit. If you kept a database of serial numbers, you'd
         | additionally need to store who has which bill or you'd still
         | not know whether you're the sole owner of this serial number.
        
           | someguyorother wrote:
           | Couldn't the central bank just sign the fingerprint and print
           | the signature on the note? If the fingerprint can't be
           | counterfeited and the private key can't be stolen, then the
           | note would be unforgeable. As long as the fingerprint is
           | robust enough.
        
             | mattnewton wrote:
             | This was my thought, but with a central database of serial
             | -> fingerprint. I like yours because of the distributed
             | nature.
        
         | thatguy0900 wrote:
         | I assume they would fingerprint every note at manufacture, then
         | compare every note at purchase time to see if it matches a
         | known good fingerprint. You would need to completely remake all
         | bills in circulation with a new style and make invalid the old
         | style, and equip everyone that takes cash with a fingerprint
         | machine. If they tried to just slowly scan in existing bills
         | people would just keep making the fakes, I would imagine.
        
           | UncleEntity wrote:
           | > You would need to completely remake all bills in
           | circulation with a new style and make invalid the old
           | style...
           | 
           | It takes a while for all the old bills to get out of
           | circulation though -- a few years ago I got my hands on a $20
           | bill from 1970 and the kid at the corner store almost didn't
           | take it since they had apparently never seen one that old,
           | probably didn't help it was nice and crisp as well. Only
           | thing I can imagine is someone was saving it from their birth
           | year and had to spend it for whatever reason since $20 in
           | 1970 was over $100 in today's dollars so they lost a bunch of
           | value holding that bill.
        
           | mannykannot wrote:
           | You do not have to equip everyone who takes cash with a
           | scanner, as banknotes regularly circulate through banks.
           | 
           | I do not know how, and how frequently, current anti-
           | counterfeiting measures are checked, but the more subtle of
           | them are almost never checked in ordinary cash transactions.
           | Presumably they are checked somewhere?
        
             | thatguy0900 wrote:
             | I would imagine the only time it is important to stop a
             | counterfeit bill is the first time its used, right? If the
             | goal is to stop people from counterfeiting, at least.
        
         | w0mbat wrote:
         | I am not convinced that the texture fingerprint is robust
         | enough to remain unchanged once the note goes out into the
         | world and is circulated for a while. Notes would start to be
         | rejected as not matching the factory fingerprint just from
         | normal wear.
        
           | rlpb wrote:
           | The article covers this concern, and the claim there is that
           | they have verified that regular wear and tear does not
           | tarnish the fingerprint.
        
       | psychlops wrote:
       | I was curious so checked and thought other might be interested.
       | 
       | https://www.bankofengland.co.uk/banknotes/counterfeit-bankno...
       | 
       | "How many counterfeit banknotes are in circulation?
       | 
       | The vast majority of counterfeits are discovered before they go
       | back into circulation, when retailers and the banking system are
       | sorting them. A smaller number are detected by the public or
       | retailers who hand them directly to the police, or when the
       | police carry out search warrants. Counterfeits are typically
       | removed from circulation quickly, often after a single use.
       | 
       | Only a small fraction, typically less than 0.02% of banknotes are
       | counterfeit, that is less than 1 in 5,000 banknotes. In the first
       | half of 2020, around 94,000 counterfeit Bank of England banknotes
       | with a face value of PS2.1 million were taken out of circulation.
       | At any one time, there is an average of 4 billion genuine
       | banknotes in circulation, with a notional face value of around
       | PS75 billion."
       | 
       | The scope of the problem seems to be about 2 million pounds per
       | year. I wonder what this solution will save and cost.
        
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